Textures and the Lighting Effects filter can
make an image jump right off the page or screen. Using a texture
to create 3D, however, is a scary thing for most Photoshop
users. We'll take some of the mystery out of the process.
Before we get into the nuts and bolts of this
week's column, I'd like to take a moment to congratulate Adobe
Systems, Inc. on the successful release of Photoshop 6. The
product has started arriving and is being put into production.
And, judging from the nature of the requests for assistance I've
received, the transition is going smoothly for most. (The
problems that have arisen are, almost exclusively, user
inexperience or hardware issues.)
I'd also like to congratulate Adobe for its
support of The Hunger Site (www.thehungersite.com), a
worthwhile, United Nations-affiliated project that supplies food
to hungry people around the world. The Hunger Site is just one
of the causes that receives support from Adobe -- check out
www.adobe.com/aboutadobe/philanthropy/main.html to learn
more.
I jokingly pointed out to a colleague recently
that Photoshop has a specific learning pattern for most users:
--Get scared of the Pen tool. Learn to use the Pen tool.
--Get scared of Levels. Learn to use Levels.
--Get scared of Masks. Learn to use Masks.
--Get scared of Curves. Learn to use Curves.
--Get scared of Color Management. Stay scared of Color
Management.
--Get scared of Channels. Learn to use Channels.
--Get scared of Textures. Learn to use Textures. In this column,
we'll try to start the process of getting un-scared of Textures,
just in time for Halloween.
Textures are grayscale images that can be used
by certain features in Photoshop to represent 3D (among other
functions). The primary employer of Textures as 3D in this
manner is Lighting Effects (Filter> Render> Lighting
Effects...). This filter uses variations in color to represent
variations in "elevation" of an image. We'll use the analogy of
elevation, such as that in a relief map, throughout this
discussion.
Think of land, in reality and as represented on
a map, as consisting of points above ground level (hills and
mountains, primarily) and points below ground level (valleys,
bottoms of lakes and oceans, riverbeds). If we think globally,
we can think of "sea level" as the average, with mountains being
higher and oceans being lower. This leads to the key
relationship among grayscale colors in a texture:
--"Sea Level," ground zero, is a grayscale value of 128.
--"Mountains," areas above sea level, range from 129 to 255.
--"Oceans," areas below sea level, range from 127 to 0.
--The farther the gray of an area if from 128, the more extreme
the "elevation."
Figure 1 shows a texture image set up to
demonstrate how this works. The background is neutral gray, with
an RGB value of 128/128/128. The triangles and their labels were
also colored using RGB values. Each of the three component
colors was set to the value shown to create the appropriate
shade of gray. For example, the triangle labeled 170 has a color
value of R-170/G-170/B-170. Using the grayscale slider in the
Color Palette, this is equivalent to 40%. (Note that 50% gray
using the slider has an RGB value of 147/147/147.) The triangles
on the right are white and black, with respective values of
255/255/255 and 0/0/0. The gradated image has a standard
black-to-white gradient.
To the far left are the first triangles in the
series. On top is a triangle (and label) filled with a gray
value of 130. This is difficult to see because the background is
128 gray. The 2-point variation is virtually imperceptible.
Below is a barely-visible triangle and label with values of 125.
The 3-point difference can be picked up by the human eye.
To prepare this image for use as a texture, it
must first be flattened and saved as a grayscale psd file.
Images in other color modes cannot be used. To use a texture
with the Lighting Effects filter, it must appear in the target
image as an Alpha channel (a mask).
--Open the target image.
--Open the grayscale texture file.
--Open the texture file's Channels palette.
--Drag the only channel available from the texture image onto
the target image and release.
--The channel appears in the Channels palette of the target
image as Alpha Channel, and it active and visible. Figures 2
through 4 show the progression.
Dragging the Gray channel.
After the channel is dropped, it become active
and visible.
Click on the RGB channel to make the composite
visible and de-activate the Alpha channel.
The target image in this case consists of an RGB
image filled with red (255/0/0). We'll use the simple red fill
to show the changes in "elevation." Figure 5 shows the settings
that were used. Note that the channel Alpha 1 must be loaded in
the lower part of the dialog box. Figure 6 shows the result.
Observe how the shadow and highlight effects on
the pairs up and down triangles are of virtually the same
magnitude, and are reversed. With the settings shown in Figure
5, the left-most triangles and labels are now visible. However,
there are virtually no differences among the effect at the more
extreme "elevations." Looking at the gradated shape, you can see
that past about the halfway mark in each direction the effect
becomes uniform.
To see more clearly how changes in gray values
can produce different "elevations," the filter was undone and
re-applied. The only change that was made was a reduction in the
Flat/Mountainous slider from 76 to 2. (The slider can be seen at
the bottom of Figure 5.)
Textures in the form of images can also be
applied using Filter> Texture> Texturizer. The dialog box is
shown in Figure 8, and the result in Figure 9.
Texturizer doesn't require that the texture map
be an Alpha channel within the image. Rather, the Load Texture
button allows you access to any .psd image. Results are far more
predictable with grayscale, but color images can also be used as
textures with the Texturizer.
Part 2 of this two-part series will look at
using textures and the Lighting Effects filter with photographic
images.
SIX SHOOTERS
• When upgrading to Photoshop 6, if the installer asks for the
CD of your previous version, look for the Eject button.
• There have been a couple of reports of conflicts with ATI
All-in-Wonder video cards. At least one successful resolution of
conflict came by setting the card to 28 bpp.
• The Photoshop Preference menu has moved. You'll now find it
under Edit, rather than 5.5's location under the File menu.
• For Mac users, the preferences file has also moved. It's back
in the System folder, inside the Preferences folder. |